Last week, private equity firms CVC Capital Partners, Kohlberg Kravis Roberts and The Blackstone Group admitted they were at the "preliminary stages of assessing Sainsbury's".
Since then a number of private equity firms have also been reported as interested in making a rival bid for the retailer, including Cinven, Apax and Texas Pacific Group.
French supermarket group Carrefour could also be eyeing the chain, according to reports in the Daily Mail.
Yesterday, Delta Two Limited, a group of investors from Qatar, revealed it had bought 300,000 Sainsbury's shares. It has the option to acquire 17 million more, bringing its stake to 1%.
Investment bank UBS also placed 15.6 million shares, raising around £80m.